The invention relates to photography and cameras and more particularly relates to a camera frame assembly having a four-bar linkage shutter actuator.
Many cameras, particularly one-time-use cameras, have single bladed impact shutters. This type of shutter has a shutter blade that pivots about a point offset from an exposure opening. The shutter blade has a first portion that covers an exposure aperture and a second portion, on the other side of the pivot point, that is struck to momentarily open the shutter. The shutter blade is biased closed by a biasing spring. The shutter blade, or a lever connected to the shutter blade, is struck by a fast moving lever, often referred to as a xe2x80x9chigh energy leverxe2x80x9d. Some other impact shutters operate in a similar manner, but have more than one blade.
Energy is typically supplied to a high energy lever by one or more springs that are biased (also referred to as xe2x80x9cchargexe2x80x9d) by a film transport mechanism during the advancing of a film frame. After biasing, the high energy lever is latched by another part. The latching is released by the shutter release. The location and operation of a high energy lever in a camera are, thus, constrained by required interactions with other camera components. Many cameras have high energy levers that pivot a lever arm about a center point to impact the shutter. Different parts of the lever arm move at different speeds. This is inconsequential if the lever arm is relatively short, but can be problematic if the lever arm is long. U.S. Pat. Nos. 3,512,466 and 4,595,269 disclose one solution to this problem. In these patents the high energy lever is a flattened plate that has a lower surface that is slid over a camera frame member. The lever arm of the high energy lever translates against the shutter blade to trip the shutter. Sliding parts have a risk of skewing relative to the direction of travel and can be subject to a large amount of friction. Bending can be a risk if weight is reduced to cut inertia.
U.S. Pat. No. 4,725,864 discloses a variable focal length camera which has a main lens system and an auxiliary lens system that can be pivoted into the optical path. The camera has a parallelogramic link mechanism that connects the camera body to a charge lever. The charge lever is slotted. Within the slot rides a pin of a set plate. The set plate and a shutter mechanism move forward and back, relative to the camera body, with other parts of a lens barrel. To charge the shutter, one of the parts of the link mechanism is moved, which moves the charge lever. The set plate is, in turn, moved by the charge lever. The set plate slides on a support and charges a spring that, when released, opens the shutter for picture taking. Another spring closes the shutter when exposure is completed. The charge lever provides the advantage of transferring a movement from the body forward to the variably positioned set plate. On the other hand, the charge lever acts through a sliding set plate and is part of a relatively complex mechanism that also includes both shutter opening and shutter closing springs.
It would thus be desirable to provide a camera frame assembly, which has the low friction advantage of pivoting along with rectilinear movement to impact a shutter.
The invention is defined by the claims. The invention, in broader aspects, provides a camera frame assembly that has a frame and a pair of tie bars extending outward from the frame. The tie bars each have opposed first and second ends. The first ends are spaced apart. The first ends are each pivotally joined to the frame. A parallel bar is pivotally joined to the second ends of the tie bars. The parallel bar is spaced outward from the frame. The parallel bar is movable, relative to the frame, from a charged position to a discharged position. A striker is movable with the parallel bar between the charged and discharged positions. An impact shutter is movable from a closed position to an open position by the striker.
It is an advantageous effect of the invention that an improved camera frame assembly is provided, which pivots and has rectilinear movement to impact a shutter.